Animal watering devices having heat insulated tanks are used to prevent the drinking water from freezing when the amvient temperature is below freezing. It is common practice to include electric tank heaters in animal waters to prevent the water from freezing in the winter months. Tank heaters are expensive to operate, require an external source of electric power, and do not function to keep the water in the animal watering devices cool in the summer months. Stock waterers have been constructed with tanks insulated with foam or other insulated materials for keeping the water from freezing during the winter months and cool during the summer months. Examples of animal watering devices having foam plastic insulated walls are shown by Martin in U.S. Pat. No. 3,745,977; Kapplinger in U.S. Pat. No. 4,100,885; and Schafer et al in U.S. Pat. No. 4,343,264.
Tank-type watering devices have drinking wells closed with a movable cover or lid. The animal raises the lid to provide access to the water in the drinking well. Float-type covers associated with the drinking wells are disclosed by Martin in U.S. Pat. No. 3,745,977 and Kuzara et al in U.S. Pat. No. 4,003,340.
Float valve assemblies are used to automatically maintain the level of the water in the tank. The float valve assemblies are isolated from the drinking wells with baffles that extend downwardly from the inside of the top wall of the watering devices into the water therein. The baffles extend transversely between the side walls of the tank. The baffles act as guides for directing convection circulation of the tank.